I know a lot of people like to trick out their rifles with all types of add-ons including myself, and I know a lot of people believe they've seen the ultimate add on to end all other add-ons, but man, I just found one that totally takes the cake.

This is basically the tactical version of the testicles you hang on your car. I love that it comes in two different colors too. It's a bit expensive, but for the rifle that has everything, what else are you going to do? I guess in a pinch, you can also use it as a small vertical grip.